Diborano: diferenças entre revisões

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==Estrutura e ligação==
[[Ficheiro:Diborane b2h6 bonding diagram.png|150px|left]]
A [[Ficheiro:Diborane_b2h6_bonding_diagram.png|thumb|left|Diagramafórmula de ligaçãoestrutural]] do diborano (B<sub>2</sub>H<sub>6</sub>) mostrandomostra com linhas curvas um par de [[ligação três centros dois elétrons|ligações três centros dois elétrons]], cada uma das quais consiste de um par de elétrons ligando três átomos, dois átomos de boro e um átomo de hidrogênio no meio.]]
Diborane adopts a D<sub>2h</sub> structure containing four terminal and two bridging hydrogen atoms. The model determined by [[molecular orbital theory]] indicates that the bonds between boron and the terminal hydrogen atoms are conventional 2-center, 2-electron [[covalent bond]]s. The bonding between the boron atoms and the bridging hydrogen atoms is, however, different from that in molecules such as hydrocarbons. Having used two electrons in bonding to the terminal hydrogen atoms, each boron has one [[valence electron]] remaining for additional bonding. The bridging hydrogen atoms provide one electron each. Thus the B<sub>2</sub>H<sub>2</sub> ring is held together with four electrons, an example of [[3-center-2-electron bond]]ing. This type of bond is sometimes called a 'banana bond'. The lengths of the B-H<sub>bridge</sub> bonds and the B-H<sub>terminal</sub> bonds are 1.33 and 1.19 Å respectively, and this difference in the lengths of these bonds reflects the difference in their strengths, the B-H<sub>bridge</sub> bonds being relatively weaker. The structure is [[isoelectronic]] with C<sub>2</sub>H<sub>6</sub><sup>2+</sup>, which would arise from the diprotonation of the planar molecule [[ethene]].<ref>{{ cite journal | journal = [[Journal of Physical Chemistry A|J. Phys. Chem. A]] | year = 2005 | volume = 109 | issue = 5 | pages = 798–801 | author = G. Rasul, G. K. S. Prakash, [[George Andrew Olah|G. A. Olah]] | doi = 10.1021/jp0404652 | title = Comparative ab Initio Study of the Structures and Stabilities of the Ethane Dication C<sub>2</sub>H<sub>6</sub><sup>2+</sup> and Its Silicon Analogues Si<sub>2</sub>H<sub>6</sub><sup>2+</sup> and CSiH<sub>6</sub><sup>2+</sup> | pmid = 16838949 }}</ref> Diborane is one of many compounds with such unusual bonding.<ref>{{cite journal | author= Laslo P | title= A Diborane Story | journal= Angewandte Chemie International Edition | year= 2000 | volume= 39 | pages= 2071–2072| doi= 10.1002/1521-3773(20000616)39:12<2071::AID-ANIE2071>3.0.CO;2-C | pmid=10941018 | issue= 12}} [http://www3.interscience.wiley.com/cgi-bin/abstract/72507084/ABSTRACT abstract]</ref>
The toxic effects of diborane are primarily due to its irritant properties. Short-term exposure to diborane can cause a sensation of tightness of the chest, shortness of breath, cough, and wheezing. These signs and symptoms can occur immediately or be delayed for up to 24 hours. Skin and eye irritation can also occur. Studies in animals have shown that diborane causes the same type of effects observed in humans. {{Citation needed|date=September 2009}}
People exposed for a long time to low amounts of diborane have experienced respiratory irritation, [[seizures]], fatigue, [[drowsiness]], confusion, and occasional transient tremors.-->
== References ==
<!-- Dead note "bauerb": {{cite journal| author=Bauer S.H.| title=The Structure of Diborane| journal=[[Journal of the American Chemical Society]]| year=1937 | pages=1096| volume=59| doi=10.1021/ja01285a041| issue=6 }} -->
<!-- Dead note "bauerb": {{cite journal| author=Bauer S.H.| title= Structures and Physical Properties of the Hydrides of Boron and of their Derivatives| journal=Chemical Reviews| year=1942 | pages=43–75| volume=31| doi=10.1021/cr60098a001| last2=Burg| first2=Anton B. }} -->
<!-- Dead note "syrkin": {{cite journal| author=Syrkin YK, Dyatkina ME | title=| journal=Acta Physicochim USSR| year=1941 | pages=547| volume=14}} -->
== Further reading ==
H. C. Brown "Organic Synthesis via Boranes" John Wiley, New York, 1975. ISBN 0-471-11280-1.
== ExternalLigações linksexternas ==
* [http://www.inchem.org/documents/icsc/icsc/eics0432.htm International Chemical Safety Card 0432]
* [http://box27.bluehost.com/~edsanvil/wiki/index.php?title=Diborane Computational Chemistry Wiki]
* [http://www.epa.gov/oppt/aegl/results65.htm U.S. EPA Acute Exposure Guideline Levels]
-->[[Categoria:agentesCompostos redutoresde boro]]
{{Boron compounds}}
[[Categoria:Compostos de hidrogénio]]
[[Category:Rocket fuels]]
-->[[Categoria:agentes redutores]]
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